A forum about all aspects of the construction and maintenance of the Billy Dawson inspired modified Hatz Classic biplane. Here is the place to ask your questions and get the answers from the real experts.
I am making the masters for copying the parts in my router and I am thinking about using Scotts (Hatz #86)method of attaching the L/E pieces. He notched the L/E an T/E to accept the ribs. My thinking is that this gives a secure glue joint but it does not lock the L/E into the ribs in the vertical direction as the stock isntallation. I would assume that the 1/16" sheeting will help secure the ribs in the vertical direction?
If I go this route I am going to leave the notch out of the front of the ply nose pieces to give more surface area for the T-88 to secure the L/E to the ribs.
This also makes it an easier task to form the L/E shape IMO.
Also if I am going to epoxy and nail the L/E sheeting should I make the false nose ribs out of 1/4" ply instead of the stock 1/8" ply or should I just worry about nailing at the full rib location?
Here are the masters I made for the nose ribs, they are made from 1/4" PVC. There are 2 small pilot holes in each master to acccept 2 #0 screws to attach each blank. The main nose rib and false rib masters match perectly together.
I will be making a trip to the local hobby shop and picking up enought 1/4 sq spruce to build one rib. This will let me assemble the jig while I am waiting on my wood order. I have enough 1/4 and 1/16 ply left over from R/C projects.
Later!!
Anthony
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I made all my false nose ribs out of 1/4" ply. Sounds to me like the vertical position of the LE to ribs will be locked in when you glue and clamp the LE onto the ribs. Unless I'm misunderstanding.
Thanks Nick,
If you notice I left out the notch in the leading edge of my ribs, the plans show a notch in the ribs with the L/E routed to fit into the notch. I will be leaving the back edge of the L/E flat with .200 deep x .250 wide notches cut into the L/E to accept the ribs. They will be mechanically locked into the L/E in the span wise direction but relying on the epoxy bond in the vertical direction. You wind up with the L/E at the same width but it gives you a little more surface area for bonding the 1/16" ply. I am sure this will be a good alternative.
This is the one area on building my model wings that always gave me the most trouble so I am looking at this very close to try and eliminate those issues from the start. The one thing about models that made things harder is that they were way over engineered. Most giant scale have 1/8" Balsa sheeting for the wing L/E and it can be a pain to confrom to the shape. My 1/3 scale Waco has 1/4" ply ribs and 3/8" spars, super strong but heavy for the size. The wings on the Hatz look frail in comparison.
Thanks Doug,
I am still working on the Jigs, my plans were off by almost 1/16" on the spar spacing so I corrected that. I just finished cutting the 1/8 Lexan to go over the plan. I ordered vertical clamps for the jig today. There will be a clamp at each gusset location. Should make it an easier task adding the gussets in quick succession. Nothing like trying to get something done before the epoxy kicks.
Here is a link to the clamps if anyone is interested. http://toggleclamps.biz/tg13005-vertica ... 13005.html
A little bit overkill but I hate fighting with individual spring clamps.
Later!!
Anthony
anthonyh wrote:...My thinking is that this gives a secure glue joint but it does not lock the L/E into the ribs in the vertical direction as the stock isntallation...
Anthony,
I can assure you that the joint is very strong in the vertical direction when T-88 is used. The L.E. notches provides 3 surfaces for each rib to adhere to. And then you have the ply sheeting that sandwiches the structure for additional strength. Short of a catastrophic event, the L.E. will not break off.
Thanks Scott,
I just about have my rib jig completed except for the vertical clamps which should arrive early this week. I have put way more time and effort into the jig than anticipated. I polished all 4 cut side of the Lexan block that I cut to prevent the epoxy from sticking to them. I made a blank of the front and rear spar from 1/4" PVC and have them screwed into place.
I am planning on giving the jig a good wipedown with Rain "X" to prevent the epoxy for sticking, has anyone else tried this? I know anywhere you have a scratch in the Lexan the epoxy will try to stick.
Hopefully I will be making a test rib tomnorrow.
Anthony
Be careful with application of Rain X. I'm not sure if it will transfer to the back-side of the rib and weaken the glue joint of the ply doubler.
I used acrylic sheet for my jig instead of Lexan. The blocks to hold everything in place was also acrylic and glued to the sheet with glue made for Plexiglas. No Rain X or other anti-sticking agent was used. While I had some ribs stick in the jig, I was always able to slide a putty knife under the wood to break the bond without damaging the wood.
